An EGR cooler that is equipped in an EGR device is provided in a circulation system for a cooling water that cools the cylinder block and the cylinder head of an internal combustion engine, and is configured to cool the EGR gas by heat exchange of the cooling water and the EGR gas. Since the temperature of the cooling water is low at the time of a cold start of an internal combustion engine, there is the fear that the EGR gas is excessively cooled and condensed water is generated inside the EGR cooler. When the condensed water is taken into the combustion chamber of the internal combustion engine, the condensed water makes combustion unstable and degrades operability of the internal combustion engine.
The art disclosed in Patent Literature 1 as follows restrains generation of the condensed water in an EGR cooler by restricting the flow rate of the cooling water which flows into the EGR cooler based on the operating state of the internal combustion engine.    [Patent Literature 1] Japanese Patent Laid-Open No. 2014-141891    [Patent Literature 2] Japanese Patent Laid-Open No. H10-110654